Every garden has a few plants that get special treatment. Coddled and cosseted beyond the call of duty, they fulfil a surprising corner of human need. It is usually because they demand it, sulking and even giving up any attempt to stay alive if they are not recognised as the prima donnas they long to be. These are specimen plants, only deigning to join the hoi-polloi of the garden in the way that a member of the Hollywood A-list descends on a restaurant with minders and paparazzi in tow. I have noticed that there seems to be a trend towards this kind of plants-as-pets gardening, a hybrid that takes in houseplants, conservatories and conventional specialisation.

In many ways it is, to my mind, the antithesis of gardening. It crosses the divide between horticulture and gardening. Since the beginning of the 19th century, the British have seen these two things as being one and the same, but of course they are quite different. Gardening is about making and tending gardens as places that comprise - among other things - a medley of plants. Horticulture is about tending plants, and often disregarding the garden in the name of the plant. Therein lies the fault of so many otherwise good gardens.

But - and this should blow away any risk of pomposity - horticulture is fun and incredibly rewarding. It makes us feel good to take a special plant and cater for all its whims and needs. If it is exotic, this makes our own midwinter lives a little better, too. So, I am all in favour of horticulture - as long as it is not at the expense of gardening.

I have a few plants that fit this list in my own garden, not least the Brugmansias. Our slightly weedy Brugmansia sanguinea flowered moderately well in August, producing flowers that started as pink and unfurled into orangey-yellow trumpets set against marvellously defined leaves, the veins as crisp and incised as handprinted green flock wallpaper. It will, apparently, make 30ft or more in the right conditions, but in the past five or six years has never got much above 5ft. I kept it in its pot, but moved it outside for a couple of months. It has a nasty habit of dying back with rather hysterical form, rising again next spring from a seemingly lifeless carcass.

At the end of July, I planted our Brugmansia x candida into a sheltered corner of the walled garden. It had spent the previous six years in a succession of pots in the greenhouse, outgrowing the available space. It didn't help that it changed its name from Datura halfway through this period. I had a girlfriend once who changed her name. It didn't work for me. I fell for the first name and wasn't sure I fancied this other moniker (Monica?) Maybe it happens more than I know outside my tightly sheltered world.

However, call it any name you like, I still want to care and tend for these Angels' Trumpets as best I can. As it had lived in a pot for a few years, the roots were bound. One of the main reasons for getting it outside - other than the fact that it was taking up a lot of space - was to give the roots a chance to shake themselves out. I dug it up yesterday and it has worked a treat. The roots have gone from being a dense, pot-shaped block to a fibrous mass of spreading tentacles. It grew at twice any previous rate over the past few months, although it has largely defoliated in the few frosts that we have had. This would have been reduced if I had been more attentive and bought it indoors, but the leaves will yellow and drop even in ideal conditions when they are dormant.

Brugmansias mostly come from the Andes, where they grow in wet, warm conditions. Ideally, they would never be exposed to temperatures greater than 30 C or less than 5 C. But as long as the roots do not freeze and that they get plenty of water, they are fairly robust. They really do need lots of water but I have made the mistake in the past of using compost that is too water retentive. They need the same mix and treatment as peaches or citrus plants - lots of water but very good drainage. A potting compost mixed 50 per cent volume of perlite seems about right. They also need regular feeding - once a week in growth and once a month in winter - with either a home-made liquid fertiliser or liquid seaweed.

The reason one grows the thing is for the brief show of extraordinary white trumpet flowers. These start as a tight paper spiral and twist open into a fanfare of flower before shrivelling away. Like angels, they come in serried ranks looking like the last movement of Beethoven's Ninth.

Brugmansias belong to the same family as Deadly Nightshade, and all parts of the plant are supposedly poisonous. I think as long as you do not chew on them you will come to no ill. This does, however, add a touch of spice to the already exotic. These plants are supposedly magnets for red spider mite and if you see any sign of cobwebs on them, assume the worst - although a spray with soft soap and good ventilation will help. I have found that snails are very fond of them and it is worth picking over the leaves regularly to see what assorted nasties they are harbouring. Within our organic set-up I have no intention of using prophylactic sprays to protect them.

In fact I would not normally bother to protect and nourish such foreign, finicky things in my garden. I like to grow native plants or ones that have essentially adapted to the microclimate of this garden - which, like almost everywhere else on these islands, is pretty accommodating. Within these soft parameters this garden is a robust set-up and the general attitude to any growing thing is that if you cannot take it as it is then you ain't going to make it.

But I have a soft spot for a few bits and pieces that slip through the rigour of this net. It has nothing to do with collecting and everything to do with tending something exotic. I feel the same about lilies, too, although they are pretty easy for all their incredible opulence.

For many people - including my own father - orchids were the popular choice to fit this bill and they do have a kind of opulent, degenerate heaviness - like a connoisseur's drug. However, orchids can be tricky and the average person who wants to love and cherish a special plant is likely to go for the exotic but not the bleedin' awkward. Bonsai fits the bill, although beware cheap imports - they have not been grown in this country. Even if they are a 'native' species, they are not adapted to our climate and are likely to be as fussy as a Brugmansia when it comes to overwintering outside. But it doesn't really matter what you choose for your own private exotica - we are into distinctly personal territory here - as long as it adds a bit of genuine spice to your garden.

My roots: A week in Monty's garden

I have been holding back a job for a rainy day, which, given the weather, is a bit of joke. For the past couple of years one of my favourite garden bits of kit has been the mist propagator I treated myself to out of the proceeds of the Fork to Fork TV series. It is 10ft x 3ft, a deep bed of gravel with heated cables looping through it and three nozzles stuck up in the air that shoot mist out when a bit of plastic dries - and that is the extent of my technical understanding of it.

But I know exactly the effect it has. Almost any cutting roots in the constant, delicate damp and most seeds germinate better. Propagation suddenly becomes very easy indeed. I assembled it myself, which was both a fiddle and a major triumph. It was put by the side of the greenhouse, more or less in the first position that it would fit, wedged level on scraps of wood.

Once the first few weeks of unadulterated ambition had passed, I realised it was in the wrong place. The end section of the greenhouse, separated by a door and partition, would be much better. It would be easier to keep the general atmosphere around the propagator moist and the rest of the greenhouse dry. Also, the open door tends to let in wind, which dries out the thingummy that controls the sprays. So it should be moved.

That has been the plan for two years, and now we have begun. Nowadays the greenhouse spends half its time under inches of water simply from general saturation. We needed to raise the floor up above the flood. The next job was to scoop out the gravel and the only way to do this was with an empty catfood tin, before dismantling the whole thing because it would not fit through the partition door. Remember, all this is happening inside a glasshouse. No opportunity for expressions of violent exasperation.

Hundreds of fiddly nuts and bolts and hours later and the horrible, ridiculous thing was in useless bits around me. I am ashamed that at this point I gave up and left it to Gareth to put it together again in its new position, which he did with calm efficiency. I love it again now that it is set up in its new home, although it won't get used for another month.

I noticed the other day that there is a solitary spray of primroses out on Beaufort's grave - the first of hundreds we have planted and which normally appear at the end of February. Primroses are my favourite flower. Beaufort was the dog.

Your roots: How to keep your Christmas tree looking spruce

If you are about to get your Christmas tree, it is essential to keep it as cool as possible if you do not want the needles to have entirely fallen by Christmas Day. The Norway Spruce (for it is he) is designed to cope with arctic cold and finds itself in an entirely alien atmosphere within the confines of a normal centrally heated house.

As a measure of desperate survival, it drops leaves (the needles) to reduce the rate of transpiration, doesn't know when to stop and ends up looking like a plucked turkey. If it is a bare-root tree then set it in damp sand and keep it as moist as is consistent with a living room/Christmas lights/presents, etc. The best place for it is the hallway or any other draughty spot, but remember - the cooler the better.